Conventionally, technology exists that broadcasts the same data to unspecified destinations on a network. For example, under address resolution protocol (ARP), to resolve a layer 2 address, broadcast is performed and the layer 2 address of the communication counterpart is acquired. Broadcasting places great load on the network consequent to transmission to unspecified destinations on the network.
As a technology that suppresses broadcasting, for example, one technology related to local area networks (LAN), converts at a hub connected by a communication line, a broadcast address that is from a connected terminal into a unicast address. Among tunneling technologies is a technology that uses a relay device having a layer 2 address storage function and transmits to a tunnel that is a relay destination and correlated with a layer 3 destination address, data whose layer 2 address taken in from a user terminal is a broadcast address.
Another technology has a search server that returns a result of address resolution in response to an address resolution request and when a layer 2 switch acknowledges a multicast packet for address resolution issued by a terminal, the layer 2 switch transfers the multicast packet through a given route to the search server. In a wireless LAN, yet another technology converts a broadcast address into a unicast address and transmits the unicast address if the destination terminal is registered in a layer 3/layer 2 conversion table that is at a base station and concerns wireless and wired terminals in the wireless LAN.
For examples of such technologies, refer to Japanese Laid-Open Patent Publication Nos. 2005-151598, 2002-374276, and 2007-81519; and International Publication Pamphlet No. WO2005/032073.
However, with the above technologies, if a conversion table is used and broadcast addresses are converted, when a layer 3 address for a device is changed, response to the change is delayed, resulting in invalid data and increased network load. Further, when a device is removed from the network, response to the change is delayed, resulting in increased network load. If the conversion table is periodically erased, broadcasting is performed irrespective of a conversion still being valid and consequently, the degree to which broadcasting is suppressed becomes low and network load increases.